1. Technical Field
This invention relates generally to intraocular lenses, and more particularly to an intraocular lens designed for placement in the capsular bag of a human eye.
2. Background Information
Conventional intraocular lenses designed for use as circular posterior chamber lens may employ haptics or fixation members to support the optic from the capsular bag. The fixation members may take the form of independent flexible loops such as the common J-loop configuration, for example. However, these can result in uneven pressure being exerted on the capsular bag, decentration of the lens, and related problems.
Some improved lenses include one or more fixation members disposed in a circular configuration. Once the lens is introduced into the eye and placed in the capsular bag, the fixation members abut almost the entire capsular equator to provide more intimate contact. This inhibits lens decentration while achieving more consistent bag fixation and postoperative lens stability.
Four such lenses are illustrated in an article entitled "New Concepts In Circular Posterior Chamber Lenses" appearing in the Oct. 1, 1987 issue of Ocular Surgery News. The article reports an interview with Aziz Y. Anis, MD regarding his designs in which Dr. Anis explains that the circular configuration is the same outside the eye as inside the eye instead of having a spring action that results in the lens conforming to the capsular bag once it is put in the eye. Dr. Anis explains that this feature avoids an impaction along a chord or diameter of the circular capsule rather than simple contact with its entire circumference.
However, there are certain problems with the illustrated lens designs that need to be overcome. It is normal for the capsular bag to sometimes contract, for example, and nonconforming fixation members may tend to impair this action. Consequently, it is desirable to have a circular lens with fixation members that can better accommodate contraction of the capsular bag.
In addition, the bag is not always perfectly circular. As a result, a nondeformable, circular configuration might not maintain intimate contact with the bag equator as expected. Thus, it is desirable to have a circular lens with fixation members that can better accommodate a noncircular capsular bag also.
Furthermore, the size of the capsular bag may vary from patient to patient so that it is desirable to have a lens suitable for different size capsular bags.
Moreover, the absence of a spring action may require too great a radial compressive force to deform the lens for implantation purposes as the surgeon introduces it through a small incision, with stress during and after implantation resulting. Consequently, it is desirable to have a lens that can be deformed slightly, radially as well as along the direction of the optical axis for this purpose.